A review of studies on Pichavaram mangrove, southeast India

We studied a tropical mangrove ecosystem, situated at Pichavaram, southeast India. We found 13 species of mangrove trees, with Avicennia marina and Rh izophora species predominant, besides 73 spp. of other plants, 52 spp. of b acteria, 23 spp. of fungi, 82 spp. of phytoplankton, 22 spp. of seaweeds, 3 spp. of seagrass, 95 spp. of zooplankton, 40 spp. of meiobenthos, 52 spp. of macrobenthos, 177 spp. of fish and 200 spp. of birds. The bacteria perfo rmed activities like photosynthesis, methanogenesis, magnetic behaviour, hu man pathogens and production of antibiotics and enzymes (arysulphatase, L-g lutaminase, chitinase, L-asparaginase, cellulase, protease, phosphatase). T he microzooplankton included tintinnids, rotifers, nauplius stages of copep ods and veliger larvae of molluscs, with a predominance of tintinnids. Tint inopsis spp. alone accounted for 90% of abundance. The macrozooplankton con sisted of 95% of copepods and coelenterates. The meiofauna was rich with ne matodes (50-70% of the component), followed by foramifera. The macrofauna i ncluded polychaetes, bivalves, gastropods, tanaids, isopods, amphipods, cir ripedes, crabs, hermit crabs and shrimps. The mangrove harboured a large nu mber of juvenile fishes, especially during summer and post-monsoon. The wat er was fertile and productive in having several fold-higher levels of nutri ents, microbes, plankton and other biological resources, than the adjoining estuarine, backwater and neritic environments. The gross primary productio n was 8 g cm(-3) d(-1); about 21% of which was contributed by phytoplankton of 5-10 mu m size. Unfortunately, 90% of the mangrove cover in the study a rea was degraded. Possible factors that cause degradation of the ecosystem are detailed and remedial measures suggested. Techniques for regeneration o f the degraded areas are proposed.